More on California Girls

While I was out for a walk with my brother David on Saturday, we ran into a couple of neighborhood friends.  I hadn’t seen one of them since my diagnosis and she mentioned that two of her sisters have been treated for breast cancer, one in her 50’s and one in her 60’s. Since my friend and her sisters all hail from the Philippines, her news reminded me of my California Girls post and ensuing curiosity about breast cancer rates in Asia.

1)  Together, the 15 countries in South, East, and Southeast Asia studied in a 2008 report on cancer in Asia comprise almost half the world’s population.

2)  Men in Taiwan, Korea, and Japan have the highest overall cancer incidence (# of new cases in a given period) rate in Asia, but they still trail their counterparts in the U.S. by at least one third.

3)  Women in Taiwan, Singapore, and the Philippines have the highest overall cancer incidence rate in Asia, although their U.S. sisters lead by about 25%.

4)  Taiwan (49 incidents/100,000), Singapore (48), and the Philippines (46) together have the highest rate of breast cancer in Asia. Following distantly after the top 3 are Japan (33), Malaysia (31), and Indonesia (26).  China is in 11th place with just 18 breast cancer incidents per 100,000 people.

5)  The U.S. by comparison has more than double the breast cancer incidence rate of any of the 15 Asian countries.  Reasons for the disparity?  Some possible causes could be genetic, environmental, or lifestyle-related (smoking, diet, exercise, child-bearing, breast-feeding).  The difference might also be explained by a widespread early screening effort in the U.S.

It is revelatory to note the relative order of breast cancer incidence for California-born/Asian-descent women is preserved when looking at their motherland cancer rates.  For California, in decreasing order of breast cancer rates by ancestral country of origin were the Philippines, Japan, and China.  Unfortunately, no other specific countries were enumerated, due to the innate limitations of the birth record data referenced by the study.  Within the 15 Asian country comparison, the Philippines came in at #3, Japan #4, and China #11.

Since the hereditary effect on breast cancer should be roughly equivalent for the Asia-born and California-born/Asian-descent cohorts, one can assume the incidence rate difference therefore results from the remaining possible factors.  At one end of the spectrum:

1)  The California-born Filipina, Japanese, and Chinese women together experienced not just similar but also sizable environmental and lifestyle changes (compared to the originating countries) which led to a doubling of breast cancer risk within a limited number of generations.

Or at the other end:

2)  The actual incidence rates are similar between the originating countries and the assimilated populations, but the differences in screening and reporting drive the bulk of the difference in official incidence rates.

In all likelihood, a combination of 1 & 2 creates the breast cancer incidence gap.  Either way, while the U.S. has the higher breast cancer incidence rate, sadly, the Philippines has a much lower survival rate (42% vs. 81%), largely because breast cancer is typically not detected until at a more advanced and therefore less treatable stage.

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